1. Field of the Invention
The invention relates to electronic security systems, particulary those systems which require a predetermined code to be entered by a user in order to gain access to or enable a device.
2. Prior Art
The escalating crime rate in recent years has prompted a need for increased security measures to protect personal property. A frequent target of thieves is electronic devices, such as for example, televisions, radios, microwave ovens, calculators and stereophonic systems. Due to the portability of many of these modern electronic devices, a thief can, with relative ease, resell or "fence" the stolen device after altering or destroying the manufacturer's serial number, thus rendering tracing by law enforcement agencies difficult if not impossible.
Attempts to secure electronic devices were initially directed toward mechanical means which physically lock or disable the television, calculator or the like. However, mechanical means have inherent disadvantages which serverely limit the practicality of this type of solution. For example, the mechanical means are typically expensive, and additionally eliminate or restrict portability which is a major advantage of modern electronic devices.
Electronic solutions to the problem of theft have included the use of a security code system which requires the user to input a predetermined code in order to gain access to or enable the protected device. Thus, each time a user desires to operate a device incorporating a security code system, he must input the predetermined code.
An example of an electronic system for a solid state device is disclosed in U.S. Pat. No. 4,139,864 by Schulman. The Schulman security circuit is in part formed on one of the same micro-electronic "chips" as that of the electronic device itself, thereby preventing a thief from physically bypassing the circuit. In order to enable the device, a user must key in a pass code, which when compared and matched with a preset internal code allows access to the device.
An example of an electronic security system for the control of communication signals is disclosed by Launzel, U.S. Pat. No. 4,179,733. The Launzel circuit incorporates a microprocessor which executes a predetermined sequence of operations upon the activation of the device's power switch. Once a predetermined security code has been entered by the user, the circuit compares the inputted code with a code stored in memory and if a match occurs the communication system is enabled.
Systems such as Schulman and Launzel require that the user enter the pass code each time he desires to make use of the device. For devices such as televisions, stereo receivers, microwave ovens and other related items which are frequently used sporadically during the course of a day, the requirement of entering a code each time operation is desired is extremely inconvenient. Furthermore, individuals who are not residents of the consumer's household, such as baby sitters and house guests, would have to be provided with the particular pass code in order to operate a device so protected, thereby potentially compromising security. Moreover, in a home or business equipped with several pass code protected devices known in the prior art, the requirement of remembering which pass code enables which device would likely prove intolerable. Thus, it is likely that consumers would not purchase a device which incorporates a pass code security system as was typical in the art prior to the present invention, since any security benefit would be perceived as outweighed by the inconvenience factor in using the device.
In addition, with systems such as Schulman and Launzel, it is possible for a thief to alter or destroy the serial number of a stolen device and render tracing difficult if not impossible in many cases. Furthermore, an unauthorized user could likely obtain the pass code by contacting the manufacturer of the device and representing that he is the true owner, inasmuch as the manufacturer had no straightforward method to check the credibility of the inquiring individual. Accordingly, there exists a need for a security system for electronic devices which is both secure and convenient for the user.
As will be disclosed below, the present invention overcomes the disadvantages associated with pass code systems such as Schulman, Launzel, and other prior art systems, by providing a unique security circuit which requires that a security code be entered only once in order to enable a device as long as a continuous source of power is supplied thereto.